1. Field of the Invention.
The present invention relates to methods of handling high peak pressures or shock waves in a firing chamber or gun barrel having a strength designed for a lower pressure or load and, more particularly, to a notched cartridge case that can be fired without harmful effects in such a firing chamber or gun barrel.
2. Description of the Related Art
When an explosive charge, propellant, or similar material is initiated, ignited, burned, detonated, or reacted in a closed or restricted case, container, or cavity, shock and/or pressure waves are produced which cause an unreinforced case, container, or cavity to bulge, swell, stretch, or otherwise be deformed if the loads exceed the elastic limits of the container material.
The strength of a cartridge case is tested most severely during firing. The pressure of the expanding gas imposes severe stresses on the cartridge case, and the case must be able to withstand the stresses without rupturing or being distorted to the extent that extraction of the case from the weapon is impeded. Another important factor in extraction, particularly in the case of automatic weapons having a high rate of fire, is elastic recovery of the cartridge case after firing. The case may be distorted for a brief tie measured in small fractions of a second at the moment of burning or detonation of the charge. It is vital that the case recover from distortion to its original size very rapidly if the case is to be easily extracted from the chamber as soon as the cartridge is fired.
In normal cartridge cases or containers, the chamber pressures are controlled by appropriate design of the reacting materials, the case or container, and the outer case, cavity, or tube. These designs are usually intended to provide a case which can be readily removed after functioning and replaced with another unit. This requires that no permanent deformation occur to the outer case, cavity, or barrel.
In certain outer cases, cavities, or barrels where peak design loads are low, maximum loads in the cases or containers used are accordingly limited. It would be an advance in the art of munitions and ordnance if there were a way to provide for a high-load output while using a relatively weak outer case.
Some related patents are described below.
U.S. Pat. No. 602,875 to Ross relates to a cartridge shell having a groove or depression around the side of and/or in the base of the shell with perforations in said grooves to allow air to communicate with the interior of the shell. The disclosed purpose is to increase the combustion and to more thoroughly consume the powder and its constituent gases before the latter leave the gun.
British patent No. 13,742 to Krnka is directed to forming the body of a bottle-shaped cartridge case with a circumferential groove to allow it to elongate, and with two or more grooves arranged transversely to the circumferential groove to allow the case to expand crosswise for the purpose of preventing the case from splitting transversely and longitudinally. The allowed elongation provides a rearward movement to an unlocking piece in the bolt or gun action and provides energy for unlocking the action.
U.S. Pat. No. 1,103,202 to Hoagland relates to a cartridge case design providing a "weakened" area whereby expansion of the cartridge case provides a gas seal to the rear of the cartridge case. The stretching of the wall of the shell is effected by forming longitudinal grooves or corrugations, and the cartridge design is also intended to prevent sticking of the shell in the chamber due to expansion of the case mouth into an eroded area of the barrel.
U.S. Pat. No. 1,103,203, also to Hoagland, is directed to a rimfire cartridge case design having a plurality of series of depressions near the head of the shell which stretch upon firing and leave expanding rings between contiguous series of depressions. The rings are forced into contact with the wall of the chamber back of where erosion ordinarily takes place.
U.S. Pat. No. 3,948,178 to Luther relates to a propellant-charge cartridge case comprising a stub which has a wall and at least one part provided with a resilient gas check which can be pressed against a barrel wall. The cartridge-case wall is formed with a annular groove cut from the outside to weaken the cross section of the wall. A resilient insert fills the annular groove so that as the gas pressure builds up within the case upon firing, the case stub is deformed in the region of the annular groove to reduce the size thereof and squeeze the insert out of the annular groove in a gas-sealing manner against the barrel wall.
U.S. Pat. No. 4,681,038 to Washburn is directed to an ammunition round cartridge case having a stress riser in the form of at least one elongated recess adapted for preserving the seal of ignition gases within the cartridge case during initial stages of the ignition and also adapted for allowing a splitting of the cartridge case wall surface at peak pressure during firing. The purpose is to permit easy extraction or push-through ejection of the cartridge case from the gun chamber subsequent to firing of the round. A preferred embodiment utilizes a unitary recess parallel to the longitudinal axis of the cartridge case, longer than one-half of the length and having a triangular cross section, the apex of which extends more than halfway into the wall surface of the case.
None of the patents summarized above provides solutions to the problems described at the beginning of this section.